Ion Energy Spectroscopy and its application on understanding the plasma kinetics during the Pulsed Laser Deposition of oxygen deficient single crystalline Strontium Titanate and Calcium Manganate thin films*

Ion Energy Spectroscopy (IES) is a diagnostic tool that provides information about the kinetic energy distribution of ions in a plasma. Our study focuses on the plasma produced by ablation of perovskite transition metal-oxide targets during Pulsed Laser Deposition of thin films. The energy with which the ions, in the plasma impinges on the substrate, has a profound effect on the growth dynamics of thin films. Plasma plume kinetics depends mostly on target-substrate distance, laser fluence and the interaction of the plasma with the background gas. We will present data collected using IES, that maps the ion energy distribution with respect to energy, using a differential electrostatic retarding field that selects high energy cations after the removal of anions and electrons with the help of grids located in its sensor. The “spectrum” could be used to achieve films with reproducible structure-property relation for a particular target material for various combinations of growth conditions. Metal-insulator transitions of epitaxial Strontium Titanate thin films, grown under low background gas pressure (~ 10^-7 – 10^-6 Torr) are often difficult to reproduce due to stochastic distribution of defects including cation and anion off-stoichiometry. Conducting films with oxygen vacancies have shown to have excess Strontium when grown homoepitaxially. We will present data on the kinetic energy distribution of cations as function of growth parameters and discuss their correlation with the electrical properties. We will also present similar studies on the growth optimization of oxygen deficient ultra-thin films of Calcium Manganese Oxide.